Recommendation Engine Basics — Complete Guide

Recommendation Engine Basics — Complete Guide: free step-by-step lesson with examples, common mistakes, and interview tips — part of ML.NET Tutorial on Toolliyo Academy.

8 min read Updated 8/19/2026

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ML.NET Tutorial · Lesson 51 of 100

Recommendation Engine Basics

Foundations ✓ → Models ✓ → NLP & advanced → MLOps

NLP & advanced · 3 — Recs, text, ONNX · ~6 min · Module 6: Recommendation Systems

What is this?

A recommendation engine ranks items for each user from past interactions and item metadata.

Why should you care?

AIPredict ShopNest feeds need personalized product order, not only global bestsellers.

See it live — copy this example

Use a .NET console or Web API project with Microsoft.ML. Run dotnet run after pasting.

var ml = new MLContext();
var options = new MatrixFactorizationTrainer.Options {
    MatrixColumnIndexColumnName = "UserIdKey",
    MatrixRowIndexColumnName = "ProductIdKey",
    LabelColumnName = "Rating"
};
var pipe = ml.Transforms.Conversion.MapValueToKey("UserIdKey", "UserId")
    .Append(ml.Transforms.Conversion.MapValueToKey("ProductIdKey", "ProductId"))
    .Append(ml.Recommendation().Trainers.MatrixFactorization(options));
var model = pipe.Fit(interactionData);